In the last few years, there has been extensive research activity in the
emerging area of Intermittently Connected Mobile Ad Hoc Networks
(ICMANs). By considering the nature of intermittent connectivity in most
real word mobile environments without any restrictions placed on users'
behavior, ICMANs are eventually formed without any assumption with
regard to the existence of a end-to-end path between two nodes wishing
to communicate. It is different from the conventional Mobile Ad Hoc
Networks (MANETs), which have been implicitly viewed as a connected
graph with established complete paths between every pair of nodes. For
the conventional MANETs, mobility of nodes is considered as a challenge
and needs to be handled properly to enable seamless communication
between nodes. However, to overcome intermittent connectivity in the
ICMANs context, mobility is recognized as a critical component for data
communications between the nodes that may never be part of the same
connected portion of the network. This comes at the cost of addition
considerable delay in data forwarding, since data are often stored and
carried by the intermediate nodes waiting for the mobility to generate
the next forwarding opportunity that can probably bring it close to the
destination. Such incurred large delays primarily limit ICMANs to the
applications, which must tolerate delays beyond traditional forwarding
delays. ICMANs belong to the family of delay tolerant networks (DTNs).
However, the unique characteristics (e.g., self-organizing, random
mobility and ad hoc based connection) derived from MANETs distinguish
ICMANs from other typical DTNs such as interplanetary network (IPN) with
infrastructure-based architecture. By allowing mobile nodes to connect
and disconnect based on their behaviors and wills, ICMANs enable a
number of novel applications to become possible in the field of MANETs.
For example, there is a growing demand for efficient architectures for
deploying opportunistic content distribution systems over ICMANs. This
is because a large number of smart handheld devices with powerful
functions enable mobile users to utilize low cost wireless
connectivities such as Bluetooth and IEEE 802.11 for sharing and
exchanging the multimedia contents anytime anywhere. Note that such
phenomenal growth of content-rich services has promoted a new kind of
networking where the content is delivered from its source (referred to
as publisher) towards interested users (referred to as subscribers)
rather than towards the pre-specified destinations. Compared to the
extensive research activities relating to the routing and forwarding
issues in ICMANs and even DTNs, opportunistic content distribution is
just in its early stage and has not been widely addressed. With all
these in mind, this book provides an in-depth discussion on the latest
research efforts for opportunistic content distribution over ICMANs.
